As a result of the solid state protection found on this web-page I decided to play with a
remote antenna switch which could switch up to 10 antennas via the coax.
Since several years a 4 port switch is in use. It uses the coax and it as 3 options:
1. no voltage on the coax
2. positive voltage on the centre of the coax
3. negative voltage on the centre of the coax
4. An AC voltage on the coax. This voltage is rectified at the remote antenna switch.
In the beginning I used some open frame relays, but later I switched to PCB relays using 2 x 16A contacts.
These relays are sealed and much better for outside use. Problems in the beginning occurred with the chokes.
It resulted in some nice burned PCB tracks.. Be careful with series resonances!
I cannot tell you what chokes to use as these were in my junk box.
The system can also be build in free air.
This was the one which originally used open frame relays, these were replace by the PCB relays
The final solution was the unit with the LM3914 switch outside and the LM317 as a regulated power supply inside.
Some pot-meters are needed as one needs to adjust the voltage in a way that the correct relay is activated.
Please save the pics to your computer to view them bigger.
Make sure the voltage on the coax starts well above 12V, say 15V, this leaves room for using an 7812 to regulate the voltage.
The higher voltage is than fed to a voltage divider and fed into the LM3914. In this way the supply voltage and the control voltage
can be on the same coax.
Good luck experimenting!